In the exploration and development of an oilfield, as required by technologies such as zonal testing, zonal and staged fracturing or zonal and staged production test for production zones of oil, gas and water wells, a temporary plugging process must be adopted to plug a current production zone and cut off the flowing channel of the production zone in a shaft, thereby facilitating implementation of process measures to other production zones. The temporary plugging is cancelled after the completion of the process, and the flowing channel between the production zone and the shaft is established for oil extraction and gas production on oil and gas wells.
As the most economic and effective shaft plugging technology at present, and also the most extensively used technology in shaft operation, measure innovation, and formation testing and production testing technologies, plugging with a bridge plug is one of the most extensively used processes during exploration, development and production of oil fields. However, the applicant has found that at least the following technical problems exist in a bridge plug as shown in FIG. 1 provided by the prior art. Firstly, the issue of midway setting influences normal use; regardless of a foreign product or a domestic product, the issue of midway setting frequently happens in the process of running of the bridge plug due to free movement of a bridge plug running tool and release setting of a bridge plug. Once midway setting occurs, recovery or drilling removal treatment needs to be carried out, which influences the period and costs of construction.
Secondly, recovery or plug drilling is high in cost and difficulty; restrictive conditions (e.g., settled sand, dropping objects, and well wall scale) in a shaft during plug drilling lead to more difficult plug drilling, and the shaft thus needs to be treated in advance through other processes, leading to increase in costs of construction, and even leading to complex conditions in the shaft with an influence on normal production of oil and gas wells; additionally, during plug drilling, regardless of a drillable bridge plug or a composite easy-drilling bridge plug, the drilling removal of the bridge plug itself needs a ground power system with high costs of construction on the one hand, and on the other hand, the slips of the bridge plug itself are made from a high-strength material with extremely poor drilling grindability, which becomes the most difficulty in plug drilling; the slip blocks also easily cause the issue of blockage of a plug drilling pipe column, dramatically increasing the costs of the whole plug drilling process.
Thirdly, the existing bridge plug is unstable in plugging effect after setting; the reason is that a leaking channel exists between a rubber cylinder of the bridge plug and the well wall, and the bridge plug loses its importance of plugging, resulting in unclear directions where a fracturing fluid goes and causing serious waste.
Fourthly, the bridge plug is unreliable in anchoring after setting, and goes down during fracturing, leading to a failure in zoning and having great influence on the quality of zonal fracturing construction.
Fifthly, the cage of the bridge plug cannot be adjusted in the construction site, which is inconvenient for fracturing construction.
Sixthly, the elastic sealing cylinder of the bridge plug are made from degradable rubber and degradable polymer materials, whereas the degradable rubber and the degradable polymer materials are not temperature resistant and fail in satisfying the application environments of high compressive strength; when degradable paper, degradable plastics and an imitation metal degradable material in industrial production and daily life are used for making the bridge plug, since these materials have restrictions in application range and condition in nature and are extremely low in strength, which can be only 30%-40% of the strength of a common carbon steel metal material, the bridge plug made from such materials fails in satisfying the application environments of high compressive strength in the mine field.